Last March, Royal Dutch Shell said it was selling most of its stake in Canada’s oil sands, a vast project that has extracted millions of barrels of sticky, gooey hydrocarbons from the ground in a process that resembles mining more than drilling. The oil and gas giant announced that it was unloading its oil-sands assets, for $7.25 billion, so that it could double down on businesses “where we have global scale and a competitive advantage.”

Left unsaid was a deeper reason for the divestiture. Months of deliberations behind closed doors at Shell headquarters in The Hague, Netherlands, had led the top brass at the world’s largest non-state-owned oil company by sales to conclude that the energy industry was changing fundamentally—in a way that could turn the profitable…